This invention relates generally to a system for logging earth boreholes and specifically to a system which utilizes means to assist a well logging instrument to traverse highly deviated earth boreholes.
It has become relatively common within the last few years to drill wells in the search for oil and gas and the like with a portion of the well bore deviating from the usual vertical orientation thereof. The deviation or inclination may extend for a considerable distance at angles ranging to 70.degree., sometimes returning to the usual vertical orientation.
It is also well known in the art of drilling such wells to attempt the logging of the formations surrounding such boreholes with logging instruments run into the well bore on a wireline and/or a cable to perform various operations. Such tools usually depend upon the force of gravity to permit positioning of the well tool at the desired location in the well bore.
Another problem associated with such boreholes relates to the instability of some formations penetrated by the well bore, thus causing borehole diameter changes, some very abrupt. Ledges are formed, and the logging instrument frequently will lodge against them.
It is therefore the primary object of the present invention to provide a new and improved system for logging earth boreholes;
It is also an object of the present invention to provide a new and improved system for logging deviated boreholes in which it is very difficult to cause the well logging instrument to traverse the borehole simply by its own weight.
The objects of the invention are accomplished, generally, by a system which uses sliding weighted means on the cable above the well logging instrument to assist the well logging instrument in moving through such highly deviated earth boreholes.